Parents if you want to improve your child’s chances of getting into Mensa then bribe them during their IQ test, a new study suggests.

Scientists have shown that offering a financial reward for doing well can increase their score by up to 20 points on the scale where the average is 100 and Mensa membership is around 150.

The team at the University of Pennsylvania made the findings after setting out to prove that scores in the test were not just related to intelligence but also to motivation.

They looked at 46 previous studies of more than 2,000 children to see if monetary incentives had any bearing on the result.

They found that on average a financial reward improved the score by 10 points but that higher values – above $10 (about £7) – could be rewarded with a 20 point increase.

The size of the increase seemed to be proportional to the amount of reward offered.

A second study of 500 boys found that those who showed signs of boredom and lack of motivation – for example yawning or looking around during the test – scored lower test marks.

Angela Lee Duckworth, a psychologist who led the study, said: “IQ scores may predict various outcomes in life, but in part for reasons that intelligence tests weren’t designed for.

“I hope that social scientists, educators, and policy-makers turn a more critical eye to any kind of measure, intelligence or otherwise as how hard people try could be as important to success in life as intellectual ability itself.”

The findings were reported in the journal Proceedings of the National Academy of Sciences.